What the DDS service is

Hosted by a Storage Node, the Distributed Data Store (DDS) service interfaces with the Cassandra database to manage the object metadata stored in the StorageGRID Webscale system.

The DDS service also manages the mapping of S3 and Swift objects to the unique “content handles” (UUIDs) that the StorageGRID Webscale system assigns to each ingested object.

More information

Object counts
The DDS service lists the total number of objects ingested into the StorageGRID Webscale system as well as the total number of objects ingested through each of the system’s supported interfaces (S3 or Swift).

Queries
You can identify the average time that it takes to run a query against the metadata store through the specific DDS service, the total number of successful queries, and the total number of queries that failed because of a timeout issue.

Metadata protection
Object metadata is information related to or a description of an object; for example, object modification time, or storage location. StorageGRID Webscale stores object metadata in a Cassandra database, which interfaces with the DDS service.

What the nodetool repair operation is
Periodically, the StorageGRID Webscale system runs the nodetool repair operation on Storage Nodes checking for and repairing metadata replication inconsistencies that may occur over time.